Effect of nonylphenol, an industrial endocrine disruptor chemical, on the germination and development of cos lettuce (Lactuca sativa)

Abstract

Nonylphenol (NP) is a cost-effective and exceptional performing non-ionic surfactant that is increasingly being used by developing countries that experience escalating industrialisation and agricultural intensification. It is also a well-known endocrine disrupting chemical (EDC) with estrogenic effects, that is extensively researched for its effect on aquatic life and mammals. On the contrary, only a small number of studies have investigated its effect on edible plants. Studies have shown that NP can potentially reduce the yield of plants. However, little is known about the effect on contaminated edible crops, or on its mode of action. With water being the main source of NP, coupled with the deteriorating quality of irrigation water worldwide, research in this area is urgently required in the light of increased food insecurity. The aim of this study was to establish how NP affects germination and development in cos lettuce plants in a model system set-up. This was accomplished by exposing the plants to environmentally relevant concentrations of NP, whilst monitoring its effect on the plants’ morphology, physiology and ultrastructure. A germination index was developed that can be used in combination with existing germination assays to assess the potential damage caused by NP. Results also indicated that cos lettuce plant growth is strongly inhibited by NP and that its effect is most evident on the roots of the plants. Plants that were exposed to ≥3200 µg/l NP were smaller, showed reduced chlorophyll content, stunting and thickening of roots and changes in organelle viii structure, the latter established through transmission electron microscopy. Scanning electron microscopy was used to illustrate the morphology of plant membranes and how NP can cause vesicle-like protrusions to appear on its surface. This study illustrates the detrimental effects of NP on germination and growth of lettuce plants, thereby setting a platform for further studies. By creating awareness, the use of NP can be restricted, thereby contributing to the well-being of the entire ecosystem and ensuring the growth of healthy and safe edible plants.